Before you start however ask yourself why your using Processing to do this, the Swing interface provides a good way of creating GUIs for database systems quickly with relative ease, combined with Netbeans you could probably code a DB system in Swing in a couple of days.

To answer your second question you can get the data entered from a text box and send it to a database using what is known as a prepared statement with the data from the text box, your probably best doing some reading up on the JDBC connector and its functionality before you start.

2. import controlP5.*;
3. 
   
4. import de.bezier.data.sql.*;
5. 
   
6. ControlP5 controlP5;
7. 
   
8. DatabaseManager db;
9. MySQL msql;
10. 
    
11. 
    
12. Data data;
13. 
    
14. int buttonValue = 1;
15. 
    
16. boolean isOpen = true;
17. boolean isTrue;
18. boolean isOk;
19. boolean isCheck;
20. boolean isWho, isPhone;
21. 
    
22. int myColorBackground = color(0, 0, 0);
23. 
    
24. String textName;
25. String textId;
26. 
    
27. String tName, tId;
28. 
    
29. 
    
30. EntryForm entryForm;
31. 
    
32. ControlFont font;
33. 
    
34. controlP5.Button submit, submit1, submit2, submit3, submit4, submit5;
35. 
    
36. controlP5.Button label, label1, label2, label3, label4, label5;
37. 
    
38. controlP5.Button  back1, back2, back3, back4, back5;
39. 
    
40. Textfield myTextfield, myTextfield1, myTextfield2, myTextfield3;
41. 
    
42. 
    
43. CheckBox checkbox;
44. ListBox l;
45. PFont font1;
46. 
    
47. 
    
48. void setup() {
49. 
    
50.   size(1024, 768);
51.   smooth();
52.   frameRate(30);
53.   
54.   controlP5 = new ControlP5(this);
55.  
56.   PFont pfont = createFont("Arial", 12, true); // use true/false for smooth/no-smooth
57.  
58.   font = new ControlFont(pfont);
59.   
60.   font1 = createFont("Arial", 16);
61.  
62.   String user  = "root";
63.   String pass  = ""; 
64.   String database = "test";
65. 
    
66. 
    
67.   msql = new MySQL( this, "localhost", database, user, pass );  
68.   db = new DatabaseManager();
69. 
    
70.   db.connect();
71. 
    
72.   entryForm = new EntryForm();
73.   entryForm.design();
74.   
75.   data = new Data();
76.  
77. }
78. 
    
79. 
    
80. void draw() {
81. 
    
82.   background(0);
83. 
    
84.  // entryForm.check();
85.  
86. }
87. 
    
88. public void controlEvent(ControlEvent theEvent) {
89.  // println(theEvent.controller().id());
90. }
91. 
    
92. 
    
93. 
    
94. public void name(String theName){
95.  println(theName); 
96.   data.setName(theName);
97.  
98. }
99. 
    
100. public void id(String theId){
101.   println(theId); 
102.   data.setId(theId);
103. }
104. 
     
105. 
     
106. public void next(float theValue) { 
107. 
     
108.  tId = data.getId();
109.  tName = data.getName();
110.  db.storeData(tId, tName); 
111. }
112. 
     
114. class Data{
115.   
116.   public String name;
117.   public String id;
118.   
119.   Data(){
120.   }
121.   
122.   void setName(String textName){
123.     name = textName;
124.   }
125.     
126.   void setId(String textId){
127.     id = textId;
128.   }
129.   
130.    public String getId(){
131.     return id;
132.   }
133.   
134.   public String getName(){
135.     return name;
136.   } 
137.     
138. }
139. 
     
141. import java.sql.*;
142. 
     
143. class DatabaseManager{
144.   
145.  // public java.sql.Connection con;
146.  //  public java.sql.Statement st;  
147.   
148.   DatabaseManager(){
149.   }
150.        
151.   void connect(){
152.    
153.    if ( msql.connect() )
154.     {
155.         msql.query( "SELECT COUNT(*) FROM guest" );
156.         msql.next();
157.         println( "number of rows: " + msql.getInt(1) );
158.     }
159.     else
160.     { 
161.         println("connection failed !");
162.     }
163.   }  
164.   
165.  
166.   void storeData(String id, String name){
167.     
168.       
169.       if ( msql.connect() )
170.       {
171.          msql.execute("INSERT INTO guest(guest_id, name) VALUES ( "+id+" , "+name+")");
172.          println(id);
173.          println(name);
174.          println("database updated!!!");
175.       }
176.   }
177. }
178. 
     
180. 
     
181. 
     
182. class EntryForm {
183. 
     
184.   EntryForm() {
185.   }
186. 
     
187. 
     
188.   void design() {
189. 
     
190. 
     
191.     label = controlP5.addButton("Visitor Name", 200, 150, 100, 150, 30);
192.     label.setId(1);
193.     label.captionLabel().setControlFont(font);
194.     //label.captionLabel().setControlFontSize(1);   
195. 
     
196. 
     
197.     myTextfield = controlP5.addTextfield("name")
198.       .setPosition(350, 100).setSize(250, 30)
199.         .setFont(font1)
200.           .setFocus(true)
201.             .setColor(color(255, 0, 0))
202.               .setAutoClear(true).setColorCaptionLabel(255).setValueLabel("Name").setMax(50) ;  
203. 
     
204. 
     
205.     label = controlP5.addButton("Enter Id", 200, 150, 200, 150, 30);
206.     label.setId(3);
207.     label.captionLabel().setControlFont(font);
208. 
     
209. 
     
210.     myTextfield1 = controlP5.addTextfield("id")
211.       .setPosition(350, 200).setSize(250, 30)
212.         .setFont(font)
213.           .setFocus(true)
214.             .setColor(color(255, 0, 0))
215.               .setAutoClear(true).setColorCaptionLabel(255); 
216. 
     
217. 
     
218. 
     
219.     submit = controlP5.addButton("next", 0, 420, 280, 100, 25);
220.     submit.setId(5);
221.     submit.captionLabel().setControlFont(font);
222.   }
223. }

here is the actual query to send data in the database

1.   msql.execute("INSERT INTO guest(guest_id, name) VALUES ('"+id+"', '"+name+"')");